wye vs. sanitary-tee

Can a 4x4x2 Wye fitting be used on a horizontal section of a 4" drain waste to tie-in a 2" tub drain? Or should a san-tee be used?

I'd like to be able to come into the 4" waste line at a 45 degree angle, as opposed to 90, but I thought I read somewhere on here that a wye could only be used on vertical drain stacks. (searched for the thread but couldn't "re-find" it).

A tee can only be used for directional changes from horizontal to vertical. Two 45s or a wye+45 should be used for directional changes from vertical to horizontal. Atleast that is how it's done where I am, the UPC might differ on the usage on sanitary fittings.

So you want a wye+45. It will give you more play to get things lined up anyways.

Just wanted to note that both of the drain sections I am referring to are horizontal. 2" horizontal tub drain going into a 4" horizontal waste line. I'd like to tie the 2" line into the 4" line at a 45 degree angle (such as a wye fitting allows).

Hmm, I think I follow what you are trying to describe. You have a 4" horizonal drain line under the tub, and you want to use a wye to connect a drain to the tub on a 45 angle.

Usually you don't have enough room to work with to be able to install a tub drain like that, and it basically would wet vent the tub or not vent the tub at all. If I understand you correctly, you want to use a p-trap, then a 45 directly after, and run a section of pipe down to a wye below?

It sounds like a strange way of doing it to me, perhaps someone else should chime in.

If I am understanding you right, the wye is the way to go. You have a 4" horizontal run and a 2" horizontal run that you are tying together. You are not suppose to us a tee flat like that.

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Yes, this is it. I am just trying to tie together a 2 and 4 inch line (hard to understand without a picture or drawing...I should have included one). I wasn't sure if the tie-in of 2" into the 4" needed some kind of built-in sweep (like a san-tee or combo tee has) or if I could just shoot "straight in" with a wye (straight in at a 45 degree angle, that is).

But now I understand that San-tees are for changing horizontal to vertical directions.

When going from horizontal to vertical a sani-tee is used as the vertical is often the vent and you don't want the drop of the wye creating and s-trap effect. The sani-tee does not offer a lot of directional guidance and it is not needed as there is this thing called gravity that takes over.

On the horizontal without the gravity assist you need the directional guidance of the wye.

You have your usages confused. The Y or a combination Y-1/8 bend can be used ANYWHERE. It is the sanitary tee that has its usage restricted to vertical lines when used for drainage, (not venting), purposes.